Studies are proposed of the disposition and metabolism of the aromatic amines tyramine, octopamine, and tryptamine in control rats, control rats treated with monoamine oxidase inhibitors, and in hepactomized rats. The studies will use radiolabeled amines and will be done on control rats with external bile fistules and cystostomy, and on hepatectomized rats with cystostomy. Further experiments are designed to determine whether there are changes in the bloodbrain barrier of rats to these amines at different times after hepatectomy. After the complete metabolic profile of these amines has been recognized in control and in hepatectomized rats, studies will be done of the formation of the amines and their metabolites from their precursor amino acids in the two groups of animals. These studies are significant in understanding the etiology of hepatic coma since these compounds are present in increased amounts in plasma of patients with liver failure. Also, a detailed study of their metabolism in control animals is of interest since one of these amines (tyramine) triggers hypertensive attacks in individuals taking monamine oxidase-inhibting drugs, and both tyramine and phenylethylamine can trigger migraine headaches in susceptible individuals.